1. Field of the Invention
The present invention relates to a recording apparatus structured to enable the carriage that holds a recording head to perform main scanning in the direction intersecting the conveying direction of a recording medium (sub-scanning direction).
2. Related Background Art
Conventionally, the recording apparatus provided with such function as a printer, a copying machine, and a facsimile equipment, among some others, or used as an output device of a complex electronics apparatus including a computer, a word processor, or the like or used as that of a work station, has been structured to record images on a recording material (recording medium) such as a recording sheet or a thin plastic sheet in accordance with image information. An apparatus of the kind is classified into that of ink jet type, wire-dot type, thermal type, and laser beam type, among some others, by the recording method adopted for each of them.
With the serial type recording apparatus which adopts the serial scanning type that scans in the direction (main scanning direction) intersecting the conveying direction of a recording material (sub-scanning direction), images of one line portion are recorded by recording means mounted on the carriage that reciprocates in the main scanning direction. After the one line portion is completely recorded, the recording material is conveyed by a designated amount in the sub-scanning direction. Then, images of one line portion are further recorded by the aforesaid recording means. With the repetition of these operations, recording is made entirely on the recording material.
Of the above recording apparatuses, the ink jet type recording apparatus (ink jet recording apparatus) that uses the serial scanning method performs recording by discharging ink from the recording head serving as recording means to a recording material to facilitate making recording means compact for a highly precise recording of images at a high speed. There are also advantages that it can record on an ordinary paper without any particular treatment given thereto, thus making the running costs lower, and that being non-impact type, it can operate recording in a lesser amount of noise, and recording images in colors with ease using multiple color ink as well.
Particularly, recording means (ink jet recording head) of ink jet type that discharges ink by utilization of thermal energy can be manufactured easily with liquid paths arranged in high density (discharge port arrangement) by structuring on a base plate the electrothermal converting elements, electrodes, liquid flow path walls, a ceiling plate, and some others, through the semiconductor manufacturing process, such as etching, vapor deposition, sputtering, hence enabling recording means to be made compact still more.
For the recording apparatus of serial scanning type described above, it is necessary to move the recording head stably in order to obtain a clear and high quality result of recording. Therefore, the cylindrical bearing portion of the carriage must slide in a state of maintaining a specific precision with respect to the columnar guide shaft that guides the carriage. Thus, the guide shaft and the bearing portion of the carriage should be controlled to make the dimensional tolerance between them as small as possible. Particularly, for the ink jet recording method, non-contact recording should be performed with a clearance of approximately 1 mm between the recording head and recording medium, it is required to stabilize the traveling of the carriage more reliably in order to obtain recorded images in higher precision.
However, even if it is attempted to make a structure so that the dimensional tolerance is minimized between the guide shaft and the bearing portion of the carriage, there is still a need for the provision of certain clearance between them in order to enable the bearing portion of the carriage to slide on the guide shaft smoothly. Furthermore, the possible dimensional variation due to the temperature changes should also be taken into account. Then, it becomes necessary to provide a greater clearance here. Now, even when the guide shaft and the bearing portion are formed by the material that may present a smaller dimensional variation resulting from the temperature changes, the clearance should become approximately 50 μm at the maximum including the processing tolerance. As a result, for the recording apparatus of 600 dpi (600 pixels per inch (2.54 cm)), there is a possibility that deviation of one pixel or more occurs in the impact positions of ink droplets on a recording medium.